The invention relates to reinforcing fiber scrims, comprising multi-layer MD scrims (multiaxial scrims), which each comprise fibers arranged next to each other in a layer, wherein at least two layers are at an angle to one another in the layer plane and are connected by a fixing means.
So-called multiaxial scrims consisting of carbon fibers, for example, are used wherever extreme tensile strength is required and the weight should be as small as possible. That is why multiaxial scrims for the intended components are put into a mold after they are finished and subsequently filled out with a synthetic resin, for instance epoxy resin. Workpieces can consequently be manufactured that can take on any arbitrary shape in a single piece. Strength that is far superior to other materials is achieved in connection with this because of the fibers that are used. The strength characteristics can be significantly increased because of the special nature of the carbon fibers, so the multiaxial scrims can be used in more and more areas. Typical examples of use are as boat hulls and as installed components and superstructures in boot and ship construction. Furthermore, the multiaxial scrims can be used for wing and tail-assembly skins and fuselage shells in aircraft construction. Even for helicopters, the multiaxial scrims can be used for the construction of the rotor blades. Moreover, the possibility exists in the construction of vehicles to replace a wide range of parts of the vehicle components with molded components that consist of resinified multiaxial scrims.
A series of advantages involving, for instance, the fact that greater payload amounts with lower fuel consumption can lead to higher economic efficiency due to the low unladen weight can consequently be obtained because of the high structural strength with a low component weight, especially in vehicle and aircraft construction. The use of multiaxial scrims makes a real contribution towards the solution of ecological and economic problems as far as that is concerned. It is necessary to arrange a number of multiaxial scrims on top of one another due to the fact that compliance has to be kept with a specified material thickness in some cases.
Manufacturing multiaxial scrims in such a way that two individual scrims, each comprising individual fibers arranged next to each other in a layer, are to be folded together or wrapped at an angle of 45° as an example, was previously known with regard to this. As an alternative, the possibility exists to arrange a 0° layer in the longitudinal direction of the multiaxial scrims in addition to the two +/−45° layers.
Connecting the multiaxial scrims that are individually folded together by means of a sewing technique or a gluing technique is known with regard to this. In so far as multiaxial scrims are sewed together, special machines are required that need a substantial amount of time for the sewing. It turned out here, as a further drawback, and in fact for later use, that the manufacturing-related gaps between the scrims to be sewn lead to instability in the sewn area. This drawback does not arise when the individual fibers are arranged next to one another without gaps and are connected to one another via adhesive threads or an adhesive mesh so that they can no longer shift in the positions that have been established. Dense fiber networks that can only be penetrated with difficulty by the resin to be added arise because of that as a rule, however. On the other hand, it was noted that gaps that improve penetration of the resin arise between the individual fiber because of the insertion channels brought about during sewing. A combination of both methods could certainly be useful depending on the subsequent application, in order to obtain the required strength values, on the one hand, but to simultaneously ensure that the resin materials that are used can penetrate into all of the layers of the scrims. Alternatively, one or the other of the variants can be used depending on the intended purpose.
The multiaxial scrims can be manufactured via a cutting/folding technique, but also via a wrapping technique in which at least two tapered fiber bundles are wrapped up at a wrapping angle of +/− 45° vis-a-vis one another, for example. A possibility exists with regard to this of providing the individual scrims with adhesive threads or adhesive meshes so that the further fibers that are put on the first scrim are connected with it.
The above-mentioned processes consequently make it possible to manufacture multiaxial scrims that consist of two individual layers as a rule, or three layers if necessary, and that are called MD scrims. Because of the existing thickness of the MD scrims, a number of individual work steps are required that have to be carefully performed, on the one hand, and that take up a great deal of time, on the other hand, to achieve the desired layer thickness and advantages.